1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to image processing, and more particularly, to an image processing apparatus and a control method thereof, which can remove an afterimage.
2. Description of the Related Art
An image processing apparatus such as a television (TV) set receives an image signal from a broadcast station, or a video signal from an external image device such as a video cassette recorder (VCR), a digital versatile disc (DVD) player, a personal computer (PC), etc., and performs an image processing appropriate for the received image signal to display the image based on the processed image signal. According to the input image signal, the image processing apparatus performs the image processing including analog-to-digital (AD) conversion, decoding, etc., and performs scaling of the processed image signal to thus display the image on a screen at a proper resolution.
The image processing apparatus includes a display unit having a display screen on which images are displayed based on the image signal. The image processing apparatus displays the images on the entire screen or in partial areas of the screen, according to selection of a user. For example, in the case that an aspect ratio of a screen is 16:9 and an input image signal has an aspect ratio of 4:3, the image processing apparatus can display the image with the aspect ratio of 4:3, according to selection of a user. In this case, as shown in FIG. 1, due to a difference in the aspect ratio between the screen 11 and the image 13, the image processing apparatus does not display the image on a part of the screen 11, that is, on sides 12a and 12b of the screen having a predetermined width in the horizontal direction, but instead displays the image only on a middle area 13 of the screen.
In this state, when another image is displayed after a still image is especially displayed for a predetermined time, there may occur a phenomenon that a pattern of the previous image remains. This phenomenon is called an “afterimage” or “image sticking.” Particularly, such an afterimage can be prominent in the case that the display unit is implemented as a liquid crystal display (LCD) panel, a plasma display panel (PDP), etc. The afterimage causes the problem of damage of pixels in which the afterimage is displayed, as well as deterioration of image quality.
As a related art technology for removing the afterimage, Korea Patent Laid-Open Publication No. 2005-112251 discloses a technique for detecting a portion corresponding to an image having high luminance locally or all on the entire screen over a predetermined time and controlling the number of luminance and drive sustain pulses to prevent the afterimage and the damage of the screen.
As another related art technology, Japanese Patent Laid-Open Publication No. 2003-274315 discloses a technique for preventing an afterimage of a boundary portion and damage of the screen by moving the location of a portion at which an image exists at a predetermined interval of time.
However, these related art techniques need separate hardware or software with a complicated algorithm, which results in increased manufacturing costs.
Moreover, Japanese Patent Laid-Open Publication No. 2003-274315 has a problem in that the whole motion of the image is recognized by the eyes of a viewer, thus deteriorating the image quality.
As still another related art technology for removing an afterimage, Korea Patent Laid-Open Publication No. 2004-019747 discloses a technique for moving one pixel column of a boundary portion by one pixel to the left or right to thereby prevent an afterimage and damage of a picture.
However, Korea Patent Laid-Open Publication No. 2004-019747 has a problem in that the afterimage generated in pixels except the moved pixel column can not be removed.